Boresighting of airborne laser designation systems

• US 4,422,758 A
• Filed: 07/24/1981
• Issued: 12/27/1983
• Est. Priority Date: 07/24/1981
• Status: Expired due to Fees

• Current Assignee: Northrop Corporation
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Godfrey, Thomas E., Moesser, Lovere A.
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US06/286,415
• Time in Patent Office: 886 Days
• Field of Search: 89/41 L, 244/3.13, 244/3.16, 356/141, 356/152, 356/153, 356/154, 356/138, 356/5, 250/342, 250/341
• US Class Current: 356/152.1
• CPC Class Codes: F41G 3/326 for checking the angle between the axis of the gun sighting device and an auxiliary measuring device F41G3/323 takes precedence

Abstract

A method and apparatus is described for boresighting the sighting systems ed with a 1.06 micrometer designator laser. The method enables boresighting visual direct view optics, TV, and forward looking infrared (FLIR) sights with respect to the laser itself, without the use of external targets. The laser beam is focused onto a refractory target in the boresight device, creating very briefly an incandescent hot spot which can be "seen" by all three sensors. The radiation from this hot spot is collimated by the boresight device optics and projected back into the sights exactly anti-parallel to the laser beam. By aligning the sight reticles with this hot spot, all three types of sights are aligned relative to the laser. Since the hot flash created by the laser energy is of such short duration, the alignment can be accomplished in flight where relative motion exists between the laser designator system and the boresight module. The apparatus disclosed includes a CO₂ laser alignment fixture and a reflective collimator with a phosphor thermal imaging disk for precision alignment of the laser input and FLIR output lines of sight of the boresight module.

Claims

1. In the apparatus for boresighting laser designator/ranger devices wherein radiation from a phosphorescent refractory target is collimated and projected by boresight optics for precision alignment of the laser designator device, the improvement eliminating long-term boresighting errors due to changes in mechanical and electrical boresight components comprising:

a boresight module having

a germanium laser IR window,

a visual alignment window,

optical paths leading from each window for focusing and aligning,

an internal refractory target capable of generating visible radiation in response to laser energy;

a plurality of adjustable prism wedge windows for aligning the boresight module optical paths to said visible radiation;

a collimator unit containing

a glass reticle capable of being removed,

a fold mirror,

a parabolic mirror, and

an autocollimating mirror,

each adapted to direct light in a path from the fold mirror, to the parabolic mirror, to the autocollimating mirror and back, and the glass reticle adapted to produce both a visual image and a reflected image;

means positioning said glass reticle in the collimator infinity focal plane by coincident focusing of these two images;

means for securing a phosphorescent ceramic target in said focal plane within the collimator in lieu of the glass reticle;

means within the collimator for exciting said ceramic target to phosphorescence;

an alignment fixture containing a laser beam source and a visual alignment telescope, capable of being set parallel to each other;

means for selecting the autocollimating mirror of the collimator unit with said alignment fixture;

means for focusing the alignment fixture on the collimator phosphorescent ceramic target and for concomitantly aligning the lines of sight of the visual alignment telescope thereon to obtain parallelism between the laser beam and the alignment telescope lines of sight within alignment fixture;

means in front of the parallelized alignment fixture for replacing the collimator with the boresight;

means for axially adjusting the target and for rotating the prism optical wedges within the boresight to align all optical systems of the boresight directly to the alignment fixture laser beam; and

means for locking the optical wedges to set the focus and alignment of the boresight module so that the module is ready for boresighting the laser designator/ranger device.

2. A method for boresighting laser designator/ranger devices utilizing a boresight module having both visual and IR windows, optical paths from the windows for focusing and aligning, an internal refractory target capable of generating visible radiation in response to laser energy, and a plurality of adjustable prism wedge windows for aligning the optical paths, comprising:

securing a phosphorescent ceramic target in the infinity focal plane of a collimator containing a parabolic mirror, a fold mirror and an autocollimating mirror, each adapted to direct light in a path from the fold mirror, to the parabolic mirror, to the autocollimating mirror and back to locate said infinity focal plane;

exciting the ceramic target to phosphorescence;

focusing on said phosphorescent target an alignment fixture containing a laser beam source and a visual alignment telescope, capable of being set parallel to each other;

concomitantly aligning the lines of sight of the visual alignment telescope on the phosphorescence to obtain parallelism between the laser beam source and the alignment telescope lines of sight;

then, by using the alignment fixture, aligning the optical systems of the boresight, axially adjusting the boresight internal refractory target and rotating the prism wedges to achieve said alignment; and

locking the optical wedges to set the focus and alignment of the boresight module so that the module is ready for boresighting the laser designator/ranger device.